In optical networks, distributed control planes provide automatic allocation of network resources in an end-to-end manner. Exemplary control planes may include Automatically Switched Optical Network (ASON) as defined in G.8080/Y.1304, Architecture for the automatically switched optical network (ASON) (February 2005), the contents of which are herein incorporated by reference; Generalized Multi-Protocol Label Switching (GMPLS) Architecture as defined in Request for Comments (RFC): 3945 (October 2004) and the like, the contents of which are herein incorporated by reference; Optical Signaling and Routing Protocol (OSRP) from Ciena Corporation which is an optical signaling and routing protocol similar to PNNI (Private Network-to-Network Interface), the contents of which are herein incorporated by reference; or any other type distributed control plane for controlling network elements at one or more layers, and establishing connections there between. These control planes may be referred to as data control planes as they deal with routing signals such as Synchronous Optical Network (SONET), Synchronous Digital Hierarchy (SDH), Optical Transport Network (OTN), Ethernet, and the like. These control planes are referred to as distributed control planes in that control plane functions are allocated across multiple devices or network elements. These control planes typically use source-based routing where a source node or network element determines an overall end-to-end signaled path through the network. Examples of end-to-end signaled paths in control planes include sub-network connections (SNCs) in ASON or OSRP, label switched paths (LSPs) in GMPLS, subnetwork connection protection (SNCP), etc. All control planes use the available paths to route the services and program the underlying hardware.
In various circumstances, two signaled paths may require absolute route diversity (ARD) therebetween such as for protection and the like. In this sense, the two signaled paths can be said to be related such as two legs of an SNCP, 1+1/1:1 working and protect paths, etc. In a conventional situation, in a source-based routed, distributed control plane where the two signaled paths originated on the same source node, the source node performing path computation simply has to ensure that absolute route diversity is considered in path computation. However, consider the case in a source-based routed, distributed control plane where the two signaled paths originate on a different source node, it is not possible to ensure absolute route diversity in the path computation because the path computation is performed on the different source nodes independently. From a terminology perspective, the two signaled paths originating on the same source node and terminating on a same destination node can be referred to as a Close-Close service. The two signaled paths originating on different source nodes and terminating on different destination nodes can be referred to as an Open-Open service. The two signaled paths originating on different source nodes and terminating on a same destination node can be referred to as an Open-Close service. Finally, the two signaled paths originating on the same source node and terminating on different destination nodes can be referred to as a Close-Open service. For example, SNCP legs can be referred to as Open-Open SNCP, Close-Close SNCP, etc. Other types of services besides SNCP can also use this terminology. Also, more than two paths may be required, e.g., all SNCP configurations include two paths, but other types of services can required two or more paths that need to be diversely routed.
Disadvantageously, it is not possible conventionally to ensure absolute route diversity with Open-Open services or Open-Close services in source-based routed, distributed control planes due to the lack of information between the different source nodes during path computation.